Here is the full list of all 41 RuneSage achievements.
Opened a Lightning Chest
Learned the Earth Rune
Learned the Wind Rune
Learned the Water Rune
Learned the Sun Rune
Found the first shard of the Earth Crystal
Found the first shard of the Wind Crystal
Found the first shard of the Water Crystal
Found the first shard of the Sun Crystal
Learned the Sky Rune
Found the first shard of the Sky Crystal
Opened an Earth Chest
Opened a Wind Chest
Opened a Water Chest
Opened a Sun Chest
Opened a Sky Chest
Rebuilt the Earth Crystal
Rebuilt the Wind Crystal
Rebuilt the Water Crystal
Rebuilt the Sun Crystal
Rebuilt the Sky Crystal
Learned the Fire Rune
Opened a Fire Chest
Found the first shard of the Fire Crystal
Rebuilt the Fire Crystal
Learned the Ice Rune
Opened an Ice Chest
Found the first shard of the Ice Crystal
Rebuilt the Ice Crystal
Learned the Lightning Rune
Found the first shard of the Lightning Crystal
Rebuilt the Lightning Crystal
Completed the Storm Shield
Discovered all three parts of the map to the hidden Earth pathway
Discovered all three parts of the map to the hidden Wind pathway
Discovered all three parts of the map to the hidden Water pathway
Discovered all three parts of the map to the hidden Sun pathway
Discovered all three parts of the map to the hidden Sky pathway
Discovered all three parts of the map to the hidden Fire pathway
Discovered all three parts of the map to the hidden Ice pathway
Discovered all three parts of the map to the hidden Lightning pathway